Facsimile photo transmission and reception



Nov. 10, 1942.

FACSIMILE PHOTO TRANSMISSION AND RECEPTION J. w. cox 2,301,375

Filed Nov. 7, 1940 Sheets-Sheet l l if INVENTOR. JOHN M 60A Nov. 10, 1942. 1, W COX 2,301,375

FACSIMILE PHOTO TRANSMISSION AND RECEPTION Filed' Nov. .7.' 1940 '2 Sheets-Sheet 2 INVENTOR. HN M 50X BY WV Patented Nov. 1o, 1942 TRANSMISSION AND FACSDIILE PHOTO CEPTION John W. Cox,'Berkeley, Calif., assigner to-Radio Corporation of America, a corporation of Dela- Application Noyember 7, 1940, serial No. 364511 8 Claims. (Cl. P18-6.7) I invention'relates to the transmission and .reception oi facsimileand analogous signals.

`- An object of this invention is to transmit sig- .Qnalshavinga frequency varying with the shad- 2 ing of the subject and tomove the drum, or other scanning and recording surface, relatively past the analyzing member-.iat a rate vthat varies with theirequencyzfoithe signal.

is to accomplish the result set ...-Annthenpl?. tarta-mure previous .object by. rectifymg the and stepping-the drum or iothersurface relatively past the analyzing memberagiven amount for, each rectified cycle.-

f Anotherfobiect Y is,to p eliminate synchronizing ,Q units at the transmltterand receiver by operating .the transmission scanner and the'receiving .recorder surfaces at rates varying with the shading of. the subject. whereby proper shading is produced by controlling the time of recording the tus. Fig. 2 is an illustration of the receiving ap- Fig. 3 isa plan of the pinion and release catch o! the scanner and recording drum.

Fig. .4 is an elevation of the detent and pinion shown in Fig. 3.

Fig. 5 is a series of graphs used in explaining the operation of the invention.

In the usual facsimile apparatus, constant speed units with appropriate controls aroused at the transmitter and receiver to keep the scanner and recorder operating at proportional speeds. While accurate frequency units have been developed in the prior art, it is an advantage to omit such units from the system. because or their original and maintenance costs. In my facsimile system these speeds units are not required.

Referring to Fig. 1 of the drawings. the scanner l at the transmitter maybe of any type for producing relative motion between the pick-up and the picture or subject to be transmitted, but I have illustrated it, by way of example. as consisting of a drum 2 rotated by motor l, energized from direct current mains 4. 'This motor has a suitable resistance 5, so that it can be stopped with the current on without injury to the windings. The motor can either be geared to the drum or connected directly thereto. For simplicity of illustration I have shown the latter.

` suitable photo-electric cell` and a light source for illuminating' the elementof themsubject'jon the drum .directly beneaththe pick-urn .the photocell and ,the illuminating element well known in the art, they have not fbeenillu'shateid.

The pick-upl l2 is moved axially ofthe -drum by the usual threaded'shaft I3,"rotated by gear il meshing with a pinion I5 on the dnunshaft. The gears in the scannermay have any desired pitch, as the invention is not limited to any line advance 'or circumferential speed ofthe drum. However.. by. way of example only. it -will be assumed that when the dog 8 disengages the catch, 8 so that the pinion can makea revolution, the Ydrum 2 will be moved circumferentially oneiii'tieth of an inch and the pick-up l2 `wili'move to the right one-ilitieth of an inch for each complete revolution of the drum. That is, the line advance will be one-ftieth of an inch.

The scanning device of the recorder will be the same as that shown at the transmitter, except.

that the element i2, instead of having a photoelectric cell for conversion of varying illumination into electric currents, will have a device for converting current into either illumination or mechanical motion to produce a record. This may be produced in any of the well-known ways. but merelyby way of example it is assumed that the element 2 at the receiver contains a neon or other suitable lamp I8 for converting the sig-` nal pulses into illumination and that the drum supports a light sensitive surface for producing a picture in a suitable darkroom.

The pick-up I2 at the transmitter is adjustably connected by conductor i1 to a potentiometer resistance Il joined to the terminals of battery or other source of voltage Il. While the voltage variations produced by the photocell o the pick-up l1 can be used either to reduce or to increase the potential applied to the grid of the tube, Lhave illustrated it, by way of example. as increasing the potential. The negative terminal of the battery I9 is thus connected to the cathode of this tube. The cathode o! tube 20 is also connected through a suitable resistance 2l is madeadjustable, as shown. A condenser 2lis connected across the neon tube and the primary of transformer 24 for producing oscillations, though it could be connected in other ways to the elements illustrated without materially changing its operation.

The secondary of transformer 24 is connected to suitable amplifier stages 21 and this is connected to any type of modulator 28 for modulating the radio frequency carrier produced in transmitting apparatus 29 having an antenna 3U. The amplifier, modulator and transmitting apparatus may be of any type and hence are not illustrated in detail, since they are well known in the art. The amplifier 21 also has connected across its output terminals a load resistance 3l and a halfwave rectifier 32. To'produce momentary energization of the magnet Il, a transformer 33 and rectifier 34, like rectiiler 32 but illustrated diagrammatically, are used to energize magnet ii.l By connecting the coil Il through the rectifier 34 to the secondary of the transformer, it is energized only by a pulse induced at the beginning of the signal. This permits the dog toreturn soon after the pinion 'i starts its rotation. Ofcourse, the pulse induced in the secondary may be amplined up to any desired value for operating the magnet.

The receiving antenna 35 is connected to receiving, amplifying and detecting apparatus 38 of any well-known form and the 'audio alternating output of the receiving apparatus is fed intotransformer 31. 'I'he primary of this transformer has connected across its terminals a load resistance 38 and a half-wave rectifier 39.- It has also connected across its terminals a fullsingle-wave rectifier-may also be used, if desired;

The neon lamp I6 is adjustably connected across resistance 4I.

The operation of my invention is as follows:

The element of the subject on the drum 2 being scanned by the pick-up I2 in Fig. 1, under the values previously assumed, would be a square with sides o! one-liftieth of an-inch. The light reected from the square is converted into electric current by the pick-up l2. This will produce a certain positive potential across the 'input of vacuum tube 20, producinga given mutual conductance in the tube and causing condenser 26 tocharge at a certain rate. When this condenser is charged to the point where it can cause neon tube 23 to strike, the condenser will discharge, after which the neon tube will cease to conduct current due to the reduction of voltage across its terminals by the drop in the potentiometer resistance 25 produced by the charging current of the condenser as it commences to recharge. The shading on the elemental square of the subject will therefore produce a certain frequency.

The first` cycle of the alternating .current produced by the condenser 28 and neon tube 23, after proper amplification by amplifiers 21; is rectified by half-wave rectiiier 32 and av pulse is induced in the secondary of transformer 33 at the start of the rectined half-cycle. This pulse energizes magnet Il and releases dogl 9. This permits the motor 3 to rotate the drum 2 oneilftieth ci' an inch, whereupon the dog 8 reengages the catch 8 and stops the movement of the motor and drum. The speed of the motor is such that the pinion makes a revolution before the completion of a cycle of the highest frequency that lcan be generated in scanning the subject. The pinion, therefore. is always ready to be released at the beginning of each cycle.

The rotation of the drum 2 one-ftieth of an inch. in the example given, brings the next element under the pick-up i 2, which. it will be assumed, has an increased shade. This will produce less potential on the grid of vacuum tube 20 and the time-period of the oscillations of condenser 28 and neontube .23 will be increased; that is, the frequency will be diminished and the magnet II is re-energized after a greater interval of time. This moves the drum another one-iiftieth` of an inch by the motor 3, upon momentary release of the catch from the dog l,

`bringing the next element under the pick-up,

which may be assumed to' have a still greater shading. This will produce a still lower frequency having a greater periodic time, which will cause the drum to be stepped another element after a greater period of time. v

Thus. the drum at the transmitter isstepped -along one element at a time and the time between the individual steps of the drum depends upon the shading of the element beneath th pick-up.

'I'he frequency generated by the condenser 28 and neon tube 23 is used to modulate' the transmitter 22 and the modulated radio current is radiated by the antenna 30. 'I'he wave is re- ,ceived at the distance receiving station and ampiified and the audio frequency is extracted. The apparatus at the recorder is like that at the transmitter and therefore the recorder drum is stepped along in timed relation with the drum modulating current, this also aids in varying the shades at the recorder.

l Since the dog 8 is tripped only once each full cycle of the signal frequency, the action may take place at the end of the signal cycle as well as at the beginning. An analysis of the graphs in Fig.

5 shows how this may be easily accomplished. Graph 42 of Fig. 5 indicates the signal frequency produced by the oscillator and transmitted to the receiver. Graph 43 indicates the E. M. F. in resistance 3| if 'the positive half waves are utilized after rectification. These half waves induce in the secondary of transformer 33 an E. M. F. of the form of graph 44. Graph 45 indicates the form of the E. M. F. after rectification at 34, assuming that the negative half wave is utilized.

By reversingthe rectifier 32 so as to utilize the negative half waves of graph 42, a voltage may b'e produced in resistance 3|, 'as indicated by graph. Graph 41 will then indicate the E. M. F: induced in the secondary of transformer 33, while graph 48a will indicate the i'ectied E. M. F. in coil I I. One thus has the choice of a pulse 48 at'the beginning of a cycle of the signal, or a pulse I9 at the termination of such cycle. One also could use the positive half cycles of graph 44 and the positive half cycles of the graph 41. Both of these would be intermediate the half cycles in respect to phase.

It is practical to adjust the speed of the motor 3 so that the step by step movement of the pinion 1 and drum l2 will be substantially instantaneous if the magnet l I is so designed that it will attract or hold the armature away from catch 8 only at vthe peak voltage. The current in the photo'- electric cell I2 Will then be produced when the drum 2 is stationary, or substantially so. Various other ways may be devised to cause the pinion I to make substantially an instantaneous revolution once each signal cycle.

I have illustrated a simple mechanical catch for releasing the drum, merely to -simplify the disclosure. This may be modified in various ways without departing from the spirit. of the invention.4

Having described my invention, what I clairn is:

1. In facsimile an'd picture scanners, an optical unit having means for producing a light beam, means for causing relative movement between the subject and said beam to bring the elements of the subject successively thereinto, and means for causing said movement to be .intermittent with periods of rest varying with the density ofthe elements passing into said beam.

2. In facsimile and picture scanners, an optical unit having means for producing a light beam, means for causing relative movement between the subject and said beam to bring the elements of the subject successively thereinto, and means for causing said movement to be intermittent with constant periods of movement and periods of rest varying with the density of the elements passing into said beam. 3. In facsimile and picture scanners, a support for the subject being scanned. an optical unit having means for projecting a light beam onto said subject, means for producing relative movev ment between the support and the beam to bring the elements'of the subject successively thereinto, means for producing alternating current of frequency varying with the intensity of the light leaving .the elements when in said beam and means for stopping said movement during4 each cycle of said frequency.

4. In facsimile and picture scanners, a support for the subject being scanned, an optical unit having means for projecting a light beam onto said subject, means for producing relative movement between the support and the beam to bring the elements of the subject successively thereinto, means for producing alternating current of frequency varying with the intensity of the light leaving the elements when in said beamand means for stopping said movement during the greater part of the time period of ,each cycle of said frequency. v

5. In facsimile and picture scanners, a support for the subject being scanned, an optical unit having means for projecting a light beam onto said subject, means for producing relative movement between the support and the beam to bring the elements of the subject successively thereinto, means for producing alternating current of frequency varying with the. intensity of the light leaving the elements when in said beam, means for stopping said movement during each cycle of said frequency and means for translating the last-mentioned light beam into electrical potentials.

6. In facsimile and picture scanners, a support for the subject being scanned, van optical unit having means for projecting a light beam onto said subject. means for producing relative movement between the support and the beam to bringl the elements of the subject successively thereinto, means for producing alternating current of frequency varying with the intensity of the light. leaving the elements when in said beam, meansfor stopping said movement during each cycle oi' said frequency and means for producing electrical potentials varying with the intensity of the lastmentioned light beam.

7. In facsimile and picture "transmission, an A optical unit, means for producing intermittent relative movement between theisubject and the optical unit, the period of immobility varying with the intensity `ot `the light from said unit leaving said subject, means for producing an alternating current having a cycle for each cycle of said intermittent movement, a recorder having a support for a light sensitive surface, means for projecting a light beam onto said surface,

means for producing relative movement of said support and said ybeam and means for stopping the movement of said support during the greater part oi' -each cycle of. said frequency.

8. In facsimile and picture transmission, an optical unit, means for producing'intermittent relative movement between the subject and the optical unit,- the period of immobility varying with the intensity of the light from said unit leaving said subject, means for producing an alternating current having a cycle for each cycle of said intermittent movement,A a recorder having a support for a. light sensitive surface, means for projecting a light beam oi' constant intensity onto said surface, means for producing relative movement oi' said support and said beam and means for stopping the movement of said support during the greater frequency;

. JOHN-w. cox.

part of each cycle of saidl 

